There are known in particular inertial systems consisting of one or more sensors selected in particular from accelerometers, magnetometers or rate gyros, having one or more sensitive axes.
These inertial systems have the advantage of being autonomous and of not requiring the environment in which the motion of a mobile object is observed to be fitted out with equipment beforehand.
There is known in particular a device for sensing rotation of a solid as described in the document FR 2 838 185.
The principle of observing a mobile body in motion is to seek magnitudes representing the displacement and orientation of the mobile body, or its speed and rotation speed, or its acceleration and angular acceleration.
In practice, the sensors are placed on the observed mobile body and the aim is to determine a motion that potentially has six degrees of freedom, i.e. three degrees of freedom corresponding to the orientation of the solid in space and three degrees of freedom corresponding to the position of the mobile body.
Solving systems of equations to determine magnitudes representing the motion of a solid is generally complex and necessitates solution systems in which certain constraints are known in advance.